1. Field of the Invention
The invention relates to a seam tape and method of joining at least two substrates with the tape to provide a seam having minimum visibility. The substrates joined are typically sign faces or awnings comprising a composite of plastics and a woven scrim. The seam tape is a woven or nonwoven scrim embedded in a thermoplastic.
2. Description of the Related Art
Signs, awnings, canopies, fascia and banners (hereinafter referred to as signs) are utilized in applications requiring a strong, flexible, weather-resistant material. These signs are used indoors and outdoors and are secured to a frame such that the sign is stretched across the frame. The signs often have various color schemes and graphics emblazoned on them. The colors and graphics can be corporate logos, corporate color patterns, etc. These signs often are rendered visible from a source of backlighting which can either be natural or artificial light. The construction of the sign substrate generally involves a woven scrim sandwiched between layers of polymeric materials such as thermoplastics. The scrims are laminated to a thermoplastic such as polyvinyl chloride, polyester or polyurethane. There are various patents which describe such sign materials, including U.S. Pat. Nos. 3,523,856, 3,968,275, 4,590,027, and 4,242,380. However, one problem which has existed to date is that there is not an adequate material or method to seam these laminates without the seam area being visibly obvious to the viewer. To date, seamed laminates have utilized seam tape with a woven scrim which was very visible in the seamed laminate, thus resulting in a visible seam.
There are numerous reasons for seaming laminates. One commercially-significant reason is to adjoin smaller laminates to create large signs. There is often a need for a sign that is larger than the presently-available sign faces. Therefore, the laminates need to be pieced together to create a larger sign. Another reason to seam is that often the scrim has a visible defect produced during the weaving process. Other defects include oil, dirt, and insects which may become pressed into the laminate during the heating process These defects are currently removed from the laminate by removing a strip of material that contains the defect. This process reduces the size of the laminate, which leads to the necessity of seaming the laminate to another section of laminate.
The seam must be strong such that the seamed laminate can withstand environmental conditions, i.e., wind, rain, heat, humidity, etc. The seam also must have minimal visibility. A seam which is visible is magnified when the sign is backlit. The seam often shows up as a dark stripe, which is undesirable from an aesthetic point of view. Furthermore, signs often carry logos and colorful graphics in which visible seams can often detract significantly from the visual impact of the intended message.
To date, the above-identified problems involving the seaming of signs have not been adequately addressed. It has now been discovered that the problems of seam strength and seam visibility can be minimized through the use of a unique seam tape which adjoins sign substrates.